JavaScript Variables and Data Types Quiz

To pass the quiz, you must correctly answer at least 18 of the 20 questions below. # --quizzes-- ## --quiz-- ### --question-- #### --text-- Which of the following best describes JavaScript? #### --distractors-- A markup language used to design websites. --- A server-side programming language. --- A database management system. #### --answer-- A programming language used for web development. ### --question-- #### --text-- Which of the following is NOT a JavaScript data type? #### --distractors-- `Number` --- `Undefined` --- `Object` #### --answer-- `Double` ### --question-- #### --text-- Which of the following is NOT a valid JavaScript variable declaration? #### --distractors-- `const x = 0;` --- `let x;` --- `var x;` #### --answer-- `public Int x;` ### --question-- #### --text-- Which of the following is a common naming convention for variables in JavaScript? #### --distractors-- JavaScript case. --- Lightning case. --- Giraffe case. #### --answer-- Camel case. ### --question-- #### --text-- What is the difference between `let` and `const` variable declarations in JavaScript? #### --distractors-- `const` cannot be re-assigned nor re-declared. `let` can be re-assigned and re-declared. --- `const` can be re-assigned and re-declared. `let` cannot be re-assigned nor re-declared. --- `const` can be re-assigned but not re-declared. `let` can be re-declared, but not re-assigned. #### --answer-- `const` cannot be re-assigned or re-declared. `let` can be re-assigned, but not re-declared. ### --question-- #### --text-- Why are strings considered immutable in JavaScript? #### --distractors-- You cannot create strings using variables. --- Strings can only be created using literals. --- You can change strings, but only through global variables. #### --answer-- Once a string is created, you cannot change its characters directly. ### --question-- #### --text-- How would you print out the string `Hello, world!` in the console in JavaScript? #### --distractors-- `print("Hello, world!")` --- `alert("Hello, world");` --- `System.out.println("Hello, world!");` #### --answer-- `console.log("Hello, world!");` ### --question-- #### --text-- What does the code below do? ```js let hello = "Hello"; hello += " world"; console.log(hello); ``` #### --distractors-- Reassigns `" world"` to the variable `hello`, and prints it out in the console. --- Prints out the number of characters in `Hello world` in the console. --- Combines `"Hello"` and `" world"` into a new string and prints it, but the value of `hello` remains `"Hello"`. #### --answer-- Combines the current value of `hello` with the string `" world"`, reassigns it to `hello`, and prints it to the console. ### --question-- #### --text-- Which JavaScript character is used to mark the end of a statement? #### --distractors-- `:` --- `,` --- `.` #### --answer-- `;` ### --question-- #### --text-- Which of the following is a valid single line comment syntax in JavaScript? #### --distractors-- `# This is a single line comment` --- `-- This is a single line comment` --- `/* This is a single line comment */` #### --answer-- `// This is a single line comment` ### --question-- #### --text-- Dynamic typing in JavaScript means that: #### --distractors-- You need to declare the data type of a variable before using it. --- You cannot assign a value of one data type to a variable of a different type. --- JavaScript performs type checking before execution, meaning type related errors will be thrown before the code is run. #### --answer-- JavaScript infers the type based on the value assigned to the variable. ### --question-- #### --text-- Which of the following prints out the type of the variable `x` in the console? #### --distractors-- `console.log(x.type);` --- `console.log(typeOf(x));` --- `console.log(isNaN(x));` #### --answer-- `console.log(typeof x);` ### --question-- #### --text-- What will be the output of `console.log(typeof null);`? #### --distractors-- `"undefined"` --- `"null"` --- `"NaN"` #### --answer-- `"object"` ### --question-- #### --text-- Which of the following is a valid multi-line comment in JavaScript? #### --distractors-- ```js // This is a // multi-line // comment ``` --- ```py ''' This is a multi-line comment ''' ``` --- ```html <!-- This is a multi-line comment --> ``` #### --answer-- ```js /* This is a multi-line comment */ ``` ### --question-- #### --text-- Which of the following declares a variable in JavaScript that cannot be changed? #### --distractors-- `var x = 0;` --- `let x = 0;` --- `final x = 0;` #### --answer-- `const x = 0;` ### --question-- #### --text-- Which of the following is a valid variable name in JavaScript? #### --distractors-- `tart@n` --- `4cats` --- `!!dogs` #### --answer-- `$number` ### --question-- #### --text-- Which of the following is NOT a valid string concatenation method in JavaScript? #### --distractors-- `console.log(string1 + " " + string2);` --- `console.log("string1 " + string2);` --- `console.log(string1.concat(" ", string2));` #### --answer-- `console.log(string1 string2);` ### --question-- #### --text-- Which of the following variable names uses camel case correctly? #### --distractors-- `a_long_variable_name` --- `alongvariableName` --- `ALongVariableName` #### --answer-- `aLongVariableName` ### --question-- #### --text-- Why is it beneficial to use semicolons explicitly even though JavaScript has Automatic Semicolon Insertion? #### --distractors-- To increase the execution speed of the code. --- To maintain consistency with other programming languages. --- To allow for better debugging and error tracing. #### --answer-- To improve code readability and reliability. ### --question-- #### --text-- Which of the following is NOT a JavaScript data type? #### --distractors-- `Symbol` --- `Boolean` --- `Null` #### --answer-- `Float`